Telephone-exchange system.



E. R. CORWIN.

TELEPHONE EXCHANGE SYSTEM APPLICATION FILED MAR,3,1909,

1,071 ,209. Patented Aug. 26, 1913.

J- v y lll UNITED STATES PATENT OFFICE.

ELMER'R. CORWIN, 0F CHICAGO, ILLINOIS, ASSIGNOR TO COIQWIN TELEPHONE MANU- FACTURING COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION F ILLINOIS.

TELEPHONEEXCHANGE SYSTEM.

Specification of Letters Patent.

Patented Aug. 26,1 91.3.

Application filed March 3, 1909. Serial No. 481,082.

To all y10h-0m t may concern Be it known that I. ,ELMER Il. ConwiN,

cago, in the county of toolr and State of Illinois. have invented a certain new and useiul Improvement in Telephone-Exchange Systems. of which the following is a full, clear, concise. and exact description reference being had to the accompanying draw ings. forming a part of this specification.

My invention relates to telephone exchange systems, and has foi-,its objects. first, the provision of improved means whereby the line signal may be employed as clearingoi|t signal; second, an improvedmeans for governing the association of the opera tors telephonie outfit with the linlr connectors that are employed to unite subscribers7 lines in conversation; third, the provision of ymeans whereby the signal which is adapted to act as a line signal and a clearing-out signal is caused to givea characteristie manifestation when associated with a called line duringr the time that the call-ed subscriber allows his receiver to remain upon its switch-hook,.thereby-to inform the operator that. although tlie'signal device is conveying a signal, yet, such signal is neither a clearing-out signal nor a line sig nal, but is a calling signal, which indicates during its manifestation that the called subscriber has not responded; fourth, the provision of improved means whereby a reduced portion 0f the calling` current may be sent through the calling subscribers line to inform such calling subscriber that the called subscriber is being signaled; fifth, the provision of means whereby a source of current included with a called line for signalingpnrposes may be instantly excluded from circuit when the called subscriber responds, so as t avoid the objectioinible scund that was liitherto liable to occur: and. sixth. the provision of means for enabling the calling subscriber to disconnect the calling generator before the called subscribefs response.

()ther features and advantages of my invention will appear upon a reading ot' the following description of one embodiment of my invention'. shown in the accompanying drawing'. which indicates two telephone lines extending between sub-stations or subscribers"'stations and an exchange, at which `the limb 5 of each exchange apparatus is provided for uniting n n l Iand disconnecting telephone lines. citizen of the llnited States, residing at Chi In the embodiment vof the invention illustrated, there are two subscribers stations.

A, B, each having a telephone switch-hook 1 adapted, when holdingr the receiver Q, to inclu e a call bell 3 in bridge of the limbs l, 5 of each line, in which bridge is included a condenser 6. Other sub-station outtits may be used. 'hen the switch-hook at each station is relieved of the telephone receiver thereat, the receiver in rising opens the bell bridge and includes the telephone transmitter 7 in series `with the limbs l. 5 of the associate telephone line and in series with the receiver 2, an impedance coil 8 being then included in shunt of the telephone receiver.

.The limb 4 of each telephone line includesan electro-magnet or relay winding 9 and telephone line includes an electro-magnet or relay winding 10.v the windings-9 and 10 being upon a common magnetic core. The limbs of the telephone lines are united by a eoniinon battery 11, whereby when a receiver is removed from its switch-hook at a calling sub-station, the windings tl-and 10 are energized. 'and inasjinueh as these windings are cumulatively jwound. the core of said windings is caused to operate an armature 12, which serves to include a signal device, preferably a lamp 13, in a circuit which mav be traced from the upper terminal of theihattery 11 to the alternate contact of the armature 1'2 (by way of mechanism which will be mentioned later), the signal lain 13 corresponding to .the station froln which the telephone re- I of the battery 11.

i included in circuit, conveys a steady signal ceiver has been removed, assuming such tation to be a ealling'statioii.`a jack spring 14. a thimble 15 with which the jack switch Il is separably engaged. to the lower terminal The lamp 13, when thus to the operator, who is thereby informed that the subscriber whose line corresponds to the lamp 13 desires to initiate a call. In order that the operator may have a check upon the line signals of calling subscribers,

the circuit established through the signal device 13`for calling purposes may also include a line. pilot relay 16 common to a plurality of calling or yline signal circuits that include the devices 13.' The line pilot relay 16 has an armature, which, when circuit is closed through such pilot relay, establishes circuit through the pilot signal device 17, which is preferably a small incandescent lamp, the circuit of the line pilot signal device 17 being traceable from the upper pole of the battery 11, the armature of the line pilot relay 16, and the contact engaged by said armature when said armature is attracted, the line pilot signal device 17, to the lower pole of the battery 11.

Thel operator, in responding to the line signal, inserts the answering plug 18 into the jack of the calling subscriber, the tip of the answering plug engaging the tip line spring 19 of such jack, the sleeve of the answering plug engaging the spring 20 of such jack (the springs 19 and 20 constituing talking contact terminals of the calling line), while the heel or body of the answering plug engages the thimble 5. The spring contacts 14 and 19 are mechanically connected, so that when the tip of the answering -plug 18 engages and holds up the tip line spring-19, the contact spring 14 is elevated and maintained elevated during the presence of the answering plug in said jack, to disconnect the contact 14 from the thimble 15 and bring and maintain said contact 14 in engagement with an alternate contact 21, with results that are now to be described. As the lamp 13 and the line pilot relay 16 are in serial relation, the circuit for the line pilot relay 16 is open at the parts 14 and 15. so that when the line signal occasioned by the signal device 13 is eHaced, the circuit through the line pilot relay 16'is opened, in so far as such circuit is dependent upon continuity of the circuit through the line signal device 13, though, of course, it is apparent that the line -pilot relay 16 may continue to have its circuit closed through some other line signal device 13.

The jack associated with the line B as well as the jacks associated with other lines of the system, have parts'similar to the parts just described in connection with the jack of the line belnging to subscriber A and also has sii'nilar association with a signal device 13, the similar parts being given similar characters of reference. If the line l should happen to'he the calling line, then the answering plusr 18 would bring about the saine results which it has been described as performing in connection with the line of subscriber A.

Before proceeding with the description as to the manner in which connection is established between the subscribers, it may at this point be well to anticipate the function which the signal device 13 is adapted to perform as a clearing-out signal in association with the calling telephone line (the line ot subscriber A, for example). When the operator has inserted the answering plug, al-

though she has excluded the signal device 13 from circuit by separatigi'gathe Contact 14 from the thimble 15, yet, sl'a'e has partially established an alternate circuit for the signal device by the engagement of the contact 14 with the contact 21, and inasmuch as the contact 21 is connected by means of a conductor with the upper terminal of thebattery 11, and inasmuch as the normal contact of the associate armature 12 is connected with the lower terminal of the battery 11, the said alternate circuit for the signal device 13 is established when the subscriber at said station (A) opens the circuit 80 of the windings 9, 10 by restoring his telephone upon its switch-hook, the opening in the circuits of the windings 9, l() occurring at the sub-station, the character of such windings, as a consequence of the denergization of such windings, permitting the armature 12 to fall back to engage its normal contact, whereby the circuit for the signal device 13 partially closed by the engagement of the elements 14, 21, is completely closed by the engagement of the released armature 12 in engaging its normal contact. Thus the signal 13 is adapted at one time to present a line signal and at another time to present a clearing-out signal. A second pilot relay 22 is provided in association with the signal devices 13. which second pilot relay is included in the conductor that unites contact 21 with the upper terminal of the battery 11.y This second pilotl relay 22, by being included in the conductor that unites the contact 21 with the upper terminal of the battery 11, constitues a supervisory pilot relay, inasmuch as it depends for the continuity of its circuit upon the presence of plugs Within the jacks (in so far as the present embodiment of my invention being described is concerned). it not being my desire to limit myself to the cooperation of the plugs and jacks for the accomplishment of all ot the functions hereinbefore specified and to be specified), the presence of the plugs withih the jacks determining the alternative circuits for the signal devices 13, which includes the relay 22, 1n order that such signal devices 13 may then act as disconnect signals. The

.relay 22 is common to a plurality of signal devices 13 and may be in closed circuit if one or more of the disconnect circuits for 149 the signal devices 13 are closed, all of such disconnect signal 'circuits being necessarily opened before the circuit of the supervisory or disconnect pilotl relay 22 is opened. The disconnect pilot or supervisony relay 22 is mi) adapted to include a supervisory or disconnect pilot signal device 23 in a circuit which may be traced troni the lower terminal ot' the battery 1l, through the pilot signal 23,

the armature ot' the pilot relay 22. the con- 130 tact of the pilot relay 22, to the upper terminal of the battery 11. I thus provide what VI consider to be the novel association of a. signal device adapted to present line and disconnect signals and pilot signal devices adapted to, present line pilot signals and disconnect pilot signals, and although the electro-magnetic devices 1G and 22 (lesirably operate the pilot signal devices 17 and 23 electrically, l do not wish to be lim` ited to such a method of operation.

The presentation of the disconnect signal and the signal due to the signal device 23, may occur after the operator has answered a calling subscriber and before the operator has inserted the connecting plug within a jack of a called subscriber, if the calling subscriber happens to change his mind before the operator has had opportunity to goiconnect his line with a called subscribers line. But assuming that the calling subscriber has not restored his receiver to his switch-hook so soon, and assuming that the calling subscriber has requested connection with a called line, as, for example, the line of the subscriber B, the operator selects the mate 24 to the answering plug 18, and inserts it Within the jack of the called subscribers line, whereby the same mechanical changes are effected among the parts of the spring jack engaged by the connecting plug, so that, though circuit may be established through the windings 9 and 10 of the called subscribers line relay when the called subscriber removes his telephone from itsr switch-hook, yet, the called subscriber will notl thereby occasion the operation of the signal device 13, as a circuit connection for said signal device was previously broken at 14 and 21 by the connecting plug brought to rest with its tip in` engagement With the line spring 19. When the called subscriber is through conversation, he restores his receiver to its switch-hook, and thereby permits the armature 12 (which was attracted during the time that the called subscriber had his receiver off ofits switch-hook) to fall back, thereby to establish an alternate circuit (constituting a clearing-out circuit) for the associated signal device 13, similar to the-clearing-out circuit established for the signal device 1? associated with the line of subscriber A, to indicate to the operator that the called subscriber is through with the connection and that the connecting plug may be pulled out of the engaging jack. I do not, therefore, deem itnecessary to recite in detail the manner in which the signal device 18 illustrated at the 'right' of the. drawing acts to present a clearing-out signal due to the restoration of the receiver at the station B, as the circuit changes that are effected by the restoration of the rcceiver of the subscriber B to its switch-hook ture 12 are similar to the circuit changes concerning the signal device 13 that are effected when the receiver at the calling substation A is restored to its switch-hook. The signal device 13 in association with the line at the subscribers station B has association with the pilot relays 16 and 22 similar to the association of the signal device 13 corresponding to the line A With said pilot relays. A third function is possessed by each signal device 13 when the line associated therewith happens to be a called line, which function is to inform the operator of the presence of the receiver of the called line upon its switch-hook prior to its removal by the called subscriber in response to a call. Inasmuch as thc line and clearingout signals are unintermittently displayed by the signal devices 13, the said third flinction of said signal devices is preferably performed by causing the saine to be intermittently included in circuit. The stated third function of each signal device 1? is desirably performed by including it in a circuit which may be traced from the lower terminal of the battery 11 to the normal contact of the armature 12 ot the called subscribers line relay which is unattra cted during t-he time that the called subscriber`s receiver is upon its switch-hook. the signal device 13 associated with the called line, the contact spring 14, the contact spring 21 engaged therewith through the agency of the connecting plug, to the upper terminal of the battery 11, there being means for intermittently attracting the armature 12 during the time that. the called subscribei"s receiver is upon its hook prior to the response of the called subscriber. so as to interrupt the circuit through the lamp 1? to enable said lamp to perform the stated third function. This means, in tn'e embodiment ot the invention illustrated` resides in an intermittently operated switching device includ-- ing an intermittently actuated contact 25 and a Contact 2G intermittentl)Y engaged by the contact 25, the contacts 23. 2G being ineluded in a circuit which may belraced from the lower pole of the battery 11 through the impedance winding 2T, the contacts 25, 2Q, the sleeve of the connecting plug, the sleeve jack spring 20, the winding 10, to the upper terminal of the battery 11, The winding 1() is thus intermittently included in circuit to intermittently attract the armature 12, thereby intermittently to energize the lamp 13, so that said lamp may perform the said third function, namely, to in'l'orm the operator during -the time than the called subscriber permits his telephone to remain upon its switch-hook belrrc responding to his call.

.The features of my invent iontbus far speciically described in connection with the ac- 55 and the consequent falling back of the armacompanying drawing may be, practised in connection with any suitable form of operators telephone equipment and any suitable form of apparatus for signaling called subscribers. However, I prefer to employ the novel means illustrated and about to be described and the novel signal generator equipment and switching mechanism in association therewith for operating the signal bells at called sub-stations.

I will first refer to the control of the operators telephone equipment, which equipment is brought into service automatically, in accordance with the preferred embodiment ot' my invention, when the operator inserts an answering plug within the jack of a calling line. The operators telephone equipment includes, in the embodiment of the invention illustrated. a transmitter 2S in a local circuit including the battery 11, as will be apparent by an inspection of the diagram. there being a second local circuit for this transmitter which includes a part of the conductor of the tirety circuit and in addition a condenser' Q9 which enables this second circuit to be closed with respect to telephonic currents, but to be open with re spect to direct current to the battery 11, there being impedance coils 30 in portions of the first circuit that are not common to the second circuit for preventing the voice currents from passing away from said second circuit to which they should be preferably contined. The said second local circuit for the transmitter QS is inductively related with the circuit for the operator`s receiver 31.

The operator, upon having inserted the answering plug 18 in the jack ot' a calling subscriber. closes a local circuit through one winding a of an electro-magnet or relay` the thimble ot the iaek engaged by the plug and'the heel or body portion of the plug closing the circuit through the winding a in the embodiment of the invention illustrated, though Ido not wish to be limited to any switching device acting in cooperation with the answering plug for closing said circuit. The circuit that is established for the magnet winding a when the answering plug is inserted within the jack of the calling subscriber, may bc traced from the upper terminal of the battery 11, through the winding a, to the body of the answering plug, the thimble of the engaged jack, to the lower terminal ot' the battery 11. The adjust-ments are such, a-nd the nature of the contacts for the armature switches is such, that the electromagnet having the coil u vis only sufficiently energized when said coil a alone is included in circuit to move said armature switches indicated at l 7; sufficiently to engage the alternate contacts of said armature switches, the armature switches not being operated with sutlicient torce to move the alternate contacts far enough to permit the armature switches from Separating from their normal contacts, the normal contacts being in the nature of follow-up contacts to permit ot their continued connection with the armature switches b when said armature switches are thus partially moved when the coil (t is alone included in local circuit. The alternate contacts of the armature switches b constitute terminals of the operators telephone receiver 31 and the normal contacts 75 are connected between the condenscrs 43, whereby when the armature switches are thus partially moved, the telephone receiver 31 is connected in bridge of the talking strands of the associate cord circuit, it having been explained that when the armature switches b are only partially moved, each armature switch is simultaneously in engagement with its normal and its alternate contact for the purpose of including the operator`s` telephone circuit in bridge of thev cord circuit. lVhen the operator manipulates the connecting plug. in order to connect the calling line with the called line, ,a local circuit is established for another winding c of the relay of the electro-magnet that controls the armature switches and inasmuch as the windings a and c are cumulative, sutlicient additional tractive effort is exerted upon the armature switches to en- ,95 able them to depress the somewhat stift, though yielding, alternate contacts sulii ciently to move the armature switches b from their normal contacts. whereby the operators telephone receiver in cut out of circuit. The switching device which coperates with the connecting plug for the purpose of establishing this second local circuit for the electro-magnet governing the switches b, `is desirably present in the jack of the called subscriber that receives the connecting plug 24 (this connecting plug and the called subscribers jack coperating, as do the answering plug and the calling sub-` scribers jack, in controlling the circuits for the coils of the electro-magnet that operates switches b), the heel or body portion of the connecting plug engaging the thimble of such jack, whereby a local circuit is established for the winding c, which may be traced from the lower terminal of the battery 11` to the thimble 15 of the called subscribers jack, the body portion of the connecting plug, the said Winding c, to the upper terminal of the battery 11.

lVhen a connecting plug is inserted within the jack of a called line, the condition is such that the circuit for the signaling current is established (said circuit being preferably intermittent-ly opened and closed for the purpose of intermittently operating the `call bell at the called station), which circuit may be traced from the upper terminal of the calling generator 41 to the switch arm 25 (which is preferably employed not only to -130 intermittently include the signal device 13v the limb 4, the coil 9 of the called subscribers line relay, to the lower terminal of the calling generator 41, to operate the bell 3, the balalice of the divided current from the calling generator 41 flowing through the winding 10 of' said line relay, through the battery 11 to the same lower terminal of the generator 41. The calling generator 41 thus supplies sufficient current to operate the call bell 3 at the called station, and owing to the fact that the circuit for that portion of the calling current passing through the coil 10 of the called subscribers lilie relay is intermittently interrupted between the switch arm 25 and the lower contact therefor, the armature 12 in addition to/ being intermittently released, due to separation of the contacts 25, 26, as has been specified, is further intermittently released due to the separation of the contact 25 and the one below it, whereby circuit through the signal device 13 is not only intermittently interrupted during the absence of calling current upon the called line, but is also lntermittently interrupted during the presence of the calling current upon the called line, so that the operator cannot mistake the fiuctuating character of the signal conveyed bythe device 13. During the time that calling current is being impressed upon the called line, a portion of the current emanating from the generator 41 is'caused to pass over the calling subscribers line through the receiver at the calling subscribers station to inform the calling subscriber that the called subscribers signal bell is being operated, this small portion of the calling current flowing over the calling subscribers line until 'the called subscriber removes his telephone from its switch-hook.

v 'lo this end, a portion of the calling current flowing over the limb 4 of the called subscriber-s line is diverted from the coil 9 of the called subscribers line relay and is caused to pass through the line spring 19,

the tip of the connecting plug 24, the tip of the answering plug 1S, the 'tip spring 19 of the calling subscribers jack, the limb 4 of the calling subscribers line, the limb 5 ofthe calling subscribers line, through the winding 10 of the calling subscribers line relay (which circumstance does not affect said line relay inasmuch as it is already energized. owing to the closure of circuit therethrough at the calling subscribers station),

the battery 11, to the lower pole of the generator 41, the up er pole of said generator to the limbs 4 andp ofthe called line, to the point of connection of the lilnb 4 with the tip line spring 19. There being condensers 43 in the talking strands of the rcord circuit of proper capacity, the portion of the calling current passing over the calling subscribers line is sufiiciently reduced to prevent objectionable operation of the telephone receiver at the calling station. `Nhcn the called subscriber responds by removing his telephone from its switch-hook, circuit. is established for the relay 42, which may be traced from the lower pole of the battery 11, through the thimble 15, to the heel or body portion of the connecting plug 24, through the winding of the relay 42, the upper normal contact of said relay 42, the tip of the connecting plug 24, the tip line spring 19. the limb 4 of the called line, the transmitter and telepho-ne receiver at the called station, the limb 5 of the called line, the winding 10 of the line relay of the called line, back to the upper pole of the battery 11. The normal contact of the upper armature switch of' the relay 42 (there being one such relay 42 per link circuit) is a follow-up Contact, by which is meant that the upper yarmature switch, though moved g5 upon the energization of the relay 42, is not separated from its normal contact until after it has engaged its alternate contact, the armature switch continuing in its movement after its engagement with its alternate contact, effectively to part from the normal contact and firmly engage the alternate contact, by which operation a locking circuit is established for the relay 42 to maintain the armature switches of said relay in attracted positions so as to insure the separation of the calling generator from the called line after the called party has responded. This locking circuit may be traced from the lower pole of the battery 11, through the thimble 15, the body portion of the connecting plug 24, the winding of the relay 42, the upper armature switch of said relay, the alternate contact of said upper armature switch, to the upper terminal of the battery 11. It will be observed that the relay 42 'is instantly included in circuit lwhen the called subscriber responds whether calling current be passing over the called subscribers line or not, so that in the event of the called subture switch of the relay 42, and by providing alternative circuits for said relay 42, one to be closed first over the called subscribers line when the called subscriber responds, and the other, a local circuit, closed by the relay through itself as a consequence of this operation of the relay due to the called subscribers removal of his telephone from its switch-hook, I am enabled to use but one reimportance in telephone exchange practice,`

for by means of it I am enabled to prevent the false operation of line and disconnect signals. This feature of my invention, in order to accomplish the object stated, resides in effecting connection of the operators telephone receiver with the talking strands of the cord circuit between the condensers 43, one upon each side of each operators telephone receiver connection with `a cord strand.

'- In the embodiment of the invention illustrated, each armature switch of the structure a c is connected between a pair of condensers 43 included serially in the associate cord strand. In this way battery current is prevented from having connection with the operators telephone receiver circuit, so that the operator s telephone receiver circuit may be conductively connected between the sides of the cord strand and yet be separated from the battery by means of the condensers 43 that flank the connections of the armature switches 34, 35 with the cord strands.

I desirably provide means whereby if the calling subscriber restores his switch-hook before the called subscriber responds, the calling subscriber will thereby exclude the calling generator from circuit with the called subscribers line. The means thus employed for excluding the calling generator from the called subscriber-s line desirably also occasions the operation of the called subscribers clearing-out indicator. T0 these ends, I employ a relay Z in association with the answering end of the cord circuit and shown as being connected between the tip strand and the body strand of the cord circuit, whereby circuit is established therethrough` when the calling subscribers receiver is off of its switch-hook, which circuit may be traced from the lower terminal of the battery 11, to the thimble of the jack of the call.-

ing' subscriber, the heel or body contact of signal at 23 the answering plug 18 engaging said, thimble, the relay d, the tip of the answering plug 1S, the tip line spring of the jack receiving plug, both limbs of the calling line (assuming that the calling subscribers telephone is off of its hook) through the winding 10 of the calling subscribers line relay, to the upper terminal of the battery 11. lVhen the relay d is thus energized during the absence of the calling subscribers receiver from its switch-hook, it opens circuit througli a supplemental coil e provid cd upon the relay 42. The calling subscriber in restoring his receiver, opens the circuit for the relay 0l at his switch-hook, the armature switch of the relay d thereby being released, to establish circuit through the coil c, which circuit may be traced from the upper terminal of the battery 11, through the coil e, the

armature switch of the relay d, the heel or body contact of the plug 18, the thimble 15 engaging the same, to the lower terminal of the battery 11. If the relay 42 has not been previously energized, the coil e will energize the same so as to attract the armature switches of relay 42, whereupon the calling generator is removed from circuit relation with the called line and-the signal device 13 associated with the called line is caused to give a clearing-out signal, owing to the undisturbed -released condition ofthe armature switch 12 of the called subscribers line relay which maintains4 the circuit that causes the clearing-out signal, which circuit may be traced from the lower terminal of the battery 11 to the armature switch 12 of the called subscribers line relay, the lamp 13, the contacts 14 and'21, the supervisory pilot relay 22 (occasioning a pilot clearing-out to the upper terminal of the battery 11. means of the feature of my invention that has just been described, the operator is in position to take down a Connection, owing to the clearing-out signal manifested by the clearing-out signal device in association with the called subscribers line, which, instea'df being operated by the called subscriber, is operated/by the calling subscriber. The calling subscriber also desirably operates his own clearing-out signal whelp he restores the telephone to its switchhoo A Vhile I have herein shown and particularly described the preferred embodiment of my invention; I do not wish to be limited to the precise construction and arrangement set forth, as changes may readily be made without departing from the spirit of theinvention.

Having thus described my invention, I claim as new and desire to secure by Letters- Patent the following 1. A telephone exchange system including telephone lines extending from sub-stations to an exchange, signal devices at theexlopen at the sub-stations when the telephones thereat are restored upon their switchhooks for the purpose of conveying clearing out signals, line pilot signal mechanism common to the telephone lines and having circ-uit connections which are opened by the plugs when the line signals are effaced, and disconneet signal pilot mechanism having circuit connections Which are made When said signal devices are brought into circuit relation, that enable them to convey disconnect signals.

2, A telephone exchange system including telephone lines extending from sub-stations t0 an exchange, signal devices at the exchange, line relay apparatus in association with said telephone lines for closing circuit through said signa-l devices When calls are initiated to present line signals, switches at the exchange, link circuits having plugs for connection With telephone lines, said switches having contacts controlled by the plugs for effacing the signals presented by said signal devices, supplemental circuits .for said signal devices partially established by said plugs in coperation with said switches, and completely established by said line relays When circuits through said relays are open at the sub-stations WhenJthe telephones thereat are restored upon their switch-hooks for the purpose of conveying clearing-out signals, line pilot signal mechanisni vcommon to thel telephone lines and having circuit connections which are opened vby the plugs when the line signals are effaced, and disconnect signal pilot mechanism having circuit connections which are made when said signal devices Yare brought intocircuit relationthat enable them to convey disconnect signals.

A telephone exchange system including signal de vices in association with the lines,

apparatus whereby said signal devices may serve to convey line signals and disconnect signals, and serving to eaoe the line'signals conveyed by said signal devices and lto bring said signal devices into such associations as Twill permit them to present clearing-out signals, line pilot mechanism having circuit connections that are broken when the line ,65

signals are eaced. and supergisolw pilot c u s .K mechanism having circuit connections that-` are made when said signall devices have their circuit relations changed, to enable them to present clearing-out signals.

4. A telephone exchange system including telephone lines extending from sub-stations kto an exchange, signal devices at the ex change, line' relay apparatus in association With said telephone lines for closing circuit t-lirougli said signal devices when calls are initiated to present line signals' jack switches at the exchange to enable telephonie connection with lines, link circuits having plugs .for insertion Within said jacks, said jacks having contacts operated upon by the plugs for effacing the signals presented by said'signal devices, supplemental circuits for said signal devices partially established by said plugs in cooperation with said jacks, and completely established by said line relays When circuits through said relays are open at the sub-stations When the telephones thereat are restored upon their switch-hooks` for the purpose of conveying clearing-out signals, and apparatus for causing said signaling devices to present fluctuating signals that are different from the line signals and clearing out signals during the time that said signal devices are associated With called telephone lines at the sub-stations of which the receivers have no-t been removed' in response to calls.

5. A telephone exchange system including telephone lines extendingfrom sub-stations to an exchange, signal devices at the exchange, line relay apparatus in association with said telephone lines for closing circuit through said signal devices when calls are initiated to present line signals, switches at the exchange, link circuits having plugs for connection with telephone lines, Said switches having contacts controlled by the plugs for etfacing the signals presented by said signal devices, supplemental circuits for said signal devices partially established by said plugs in coperation with said switches, and completely established by' said line relays When circuits through saidrelays are open at the sub-stations when the telephones thereat are restored upon their switch-hooks for the purpose of conveying (clearing-out signals, and apparatus for causing said signaling devices to present fluctuating signals that are different from the line signals and clearing-out signals during the time that said signal devices are associated with called telephone lines at the sub-stations of which the receivers have not been removed lin response to calls.

6. A telephone `exchange system including telephone lines extending from sub-stations to an exchange, signal devices at the eitchange, line relay apparatus in associa-tion with said telephone lines for closing circuit through said signal devices when calls are initi ated to present line -to the telephone lines and having circuit connections which are opened by the plugs when the line signals are effaced, disconnect signal pilot mechanism having circuit connections Which are made when said signal devices are brought into circuit relation, that enable them to convey disconnect signals, and apparatus for causing said signaling devices to present characteristic signals that are different from the line signals and clear-- ing-out signals during the time that said signal devices are associated with called telephone lines at the sub-stations of which the receivers have not been removed in response to calls.

7. A telephone exchange system including telephone liiies extending from sub-stations to an exchange, signal devices at the exchange, line relay apparatus in association with said telephone lines for closing circuit through said signal devices when calls are initiated to present line signals, switches at the exchange, link circuits having plugs for connection With telephone lines, said switches having contacts controlled by the plugs for etfacing the signals presented by said signal devices, supplemental circuits Yfor said signal devices partially established by said plugs in coperation ,with said switches, and completely established by said line relays when circuits through said relays are open at the sub-stations when the telephones thereat are restored upon their switch-hooks for the purpose of conveying clearing-out signals, linepilot signal mechanism common to the telephone lines and having circuit connections which are opened by the plugs whenA the line signals are effaced, disconnect signal pilot mechanism having circuit connections which are\ made when said signal devices are brought into circuit relation, that enable them to convey disconnect signalsl fand apparatus for causing said signaling devices to present characteristic signals that are different from the line signals and clearing-cut signalsduring the time` that said signal devices are associated with called telephone lines at the sub-stations of which the receivers have not been removed in response to calls.

8. A telephone exchange system including signal devices in association with the lines, apparat-us whereby said signal devices may serve to convey 'line signals and disconnect signals, and serving to efface the line signals conveyed by said signal devices and to bring said signal devices into such associations as Will permit them to present clearing-out sig'- nals, line pilot mechanism having circuit connections that are broken when the line signals are efaced, supervisory pilot mechanism having circuit connections that are made when said signal devices have theirY circuit relations changed, t-o enable them to present clearing-out signals, and apparatus for causing said signaling devices to present characteristic signals that are dierent from the line signals and clearing-out signals during the time that Said signal devices are associated with called telephone lines at the sub-stations of which the receivers have not been removed in response to calls.

9. A telephone exchange system including telephone lines extending from sub-stations to an exchange, signal devices, means for enabling said signaling devices to serve as line and clearing-out indicators, link connectors, and means brought into association with said signal devices, when associated with called telephone lines, by said link connectors, for causing said signal devices to convey fluctuating signals to inform the operator that the called parties have not responded, lsaid latter means being governed by the called parties to efface the said characteristic signals when the called parties A respond.

1Q: A common battery telephone exchange system including telephone lines extending from sub-stations to an exchange where the common battery is provided, llink connec-.

tors for uniting said lines in conversation and each including tWo talking strands, an operators telephone outfit provided with means for bringing it in physically continuous connection between and with said talking strands, and condensers, included in said strands, one on each side of each place ot'connection of the operators telephone with said cord strands.

11. A telephone exchange system includ- 4in'.l telephone lines extending from sub-station to an exchange, apparatus for uniting telephone lines in conversation, a source of signaling current for opeiating the signal receiver at a called station, and circuit connections whereby a portion of the calling current flowing in the called line is caused to flow over the calling subscribers line to inform the calling party that a signal is being sent.

l2. A telephone exchange system including telephone lines extending from sub-stations to an exchange, cord circuits for uniting lirios in conversation, each having terminal plugs, an operators telephone, electro-magnetic mechanism for governing the association of the operators telephone with a cord circuit,A means governed by a plug for partially energizing said electro-magnetic mechanism to cause a partial operation thereof to include the operators telephone in circuit relation with the'cord circuit, and means governed by the mate, to said plug for increasing the energization of said electro-magnetic mechanism to cause it to dissociate said operators telephone from the cord circuit.

13. A'telephone exchange s vstem. including telephone lines extending from .sub-stations to an exchange, cord circuits for uniting. lines .in conversation, each having terminal plugs, an operators telephone, an electro-magnet for governing the association of the operator-s telephone with a. cord circuit, switching mechanism determining the circuit relation of the operators telephone with the cordv circuit and having three positions, firstfa normal position, in which the operators telephone is excluded from circuit, second, an intermediate position, in which the operators telephone is included in circuit, and, third, the final position, where the operators telephone is again excluded from circuit, means coperating with one of the plugs belonging to a cord circuit for placing said switching mechanism in an intermediate position, and means coperating with the mate to said plug for placing said switching mechanism in its final position.

14. A telephone exchangesystem including telephone lines extending from sub-stations to an exchange, cord circuits for uniting lines in conversation, `each having terminal plugs, an operators telephone, switching mechanism for including the operators telephone in and excluding the operators telephone from circuit, an electro-magnet for governing said switching mechanism, said electro-magnet including' cumulativ'ely wound coils, the circuit of one of which is under the control of one plug, thereby to occasion partial energization of said electro-magnet to causea partial operation of the switchingmechanism that governs the circuit relation of the operators telephone, thereby to 'connect said telephone in circuit, While the circuit of the companion coil is under the control ot the mate to the aforesaid plug further to increase the magnetization of said electro-magnet. thereby further to operate theswitching mechanism that governs the operators telephone. to remove the operators telephone from circuit relation, said electro-magnet releasing said switching mechanism when both of its coils are denergized to `permit the switching mechanism to cut the operators telephone outof circuit.

15. A telephone exchange system including telephone lines extending from sub-stations to an exchange, cord circuits for uniting lines in conversation, an operators telephone, au electro-magnet, switching mechanism including armature switches having normal follow-up contacts and yielding alternate contacts adapted with a given degree of energization of the electro-magnet, to hold said armature switches while still in engagement with their normal contacts, and means for imparting to the electro-magnet one degree of magnetization to cause the armature switches each to engage both of its contacts and an increased degree of energization to cause the armature switches further to move their alternate contacts and to separate from their normal contacts. the normal contacts of said armature switches heilig connected with the cord circuits While the alternate contacts of said armature switches con- Stitute terminals of the operators telephone.

16. A telephone exchange system including telephone lines extending from sub-stations to an exchange, cord circuits for uniting lines in conversation, an operators telephone,.an electro-magnet, switching mechanism including armature switches having normal follow-up contacts and yielding alternate contacts adapted with a given degree of energizatibh of the electro-magnet` to hold said armature switches while still in engagement with their normal contacts. and a circuit governed one of the plugs of a cord circuit for imparting partial energization to said electro-magnet, and another circuit governed by the mate to said plug for further energizing said magnet, the normal contacts of said armature switches being connected with the cord circuit while the alternate contacts of said armature switches constitute terminals of the operators telephone.

17. A telephone exchange system including telephone lines extendlng from sub-stations to an exchange, cord circuits for uniting lines in conversation, an operators telephone. an electro-magnet, switching mechanism including armature switches having normal follow-up contacts and vielding alternate contacts adapted with a given degree of encrgization of the electro-magnet. to hold said armature switches while stili in engagement with their normal contacts. means governed by one of the plugs oi' a cord circuit for imparting one degree oi' cnergization of said electro-magnet; and means governed by the mate to said plug for increasing the degree of energization of said electro-magnet.

18. A telephone exchange system including telephone lines extending from sub-stations to an exchange, cord circuits for uniting lines in conversation` each having terminal plugs, an operators telephone, electro-magnetic mechanism for governing the association ofthe operators telephone with a cord circuit, means for partially energizing said electro-magnetic mechanism to cause a partial operation thereof to include the operaorls telephone in circuit relation with the cord circuit, and means for increasing the energization of said electro-magnetic mechanism to cause it to dissociate said operators telephone from the cord circuit.

19. A telephone exchange system including telephone lines extending from sub-stations to an exchange, cord circuits for uniting lines in conversation, each having termlnal plugs, an operators telephone, an electro-magnet for governing the association of the operators telephone with a cord circuit, switching mechanism determining the circuit relation of the operators telephone with-the cord circuit and having three positions, first a normal position, in which the operator telephone is excluded from circuit, second', an intermediate position, in which the operators telephone is included in circuit', and, third, the final position, where the operators telephone is again excluded from circuit, means for placing said switching mechanism in an intermediate position, and means for placing said switching mechanism in/its final position.

20. A telephone exchange system including telephone lines extending from sub-stations to an exchange, line signal devices for said lines, a source of current, and means whereby said line signal devices are caused to present signals of special character when calling current is impressed upon a called -line.

21. A telephone exchange system including telephone lines extending'from sub-stations to an exchange, line signal devices for said lines, a source of signaling current, and means governed by a connecting plug, whereby said line signal devices are caused to present signals of special character when calling current is impressed upon a called line.

22. A telephone exchange system including telephone lines extending from sub-stations to an exchange, line signal devices for said lines, a source of current, means whereby said line signal devices are caused to present signals of special character when calling current is impressed upon a called line, and means governed by the apparatus at a called subscribcrs station whereby the aforesaid means are dissociated from a called line.

23. A telephone exchange system including telephone lines extending from sub-stations to an exchange, line signal devices for said lines, a source of signaling current, means governed by a connecting plug, whereby said line signal devices are caused to present signals of special character when lcalling current is impressed upon a called line, and means governed by the apparatus at a called station, whereby the aforesaid means are dissociated from a called line.

24. A telephone exchange system including telephone lines extending from sub-stations to an exchange, link connectors at the exchange for uniting lines in conversation, a calling generator' for operatin signal receivers at called stations, mec. anism governed at a called station ,for removing the signal generator from cireuitwith a called line, and operated when theoalled'station` responds, and means operable bythe calling station switch-hook when the receiver is placed thereupon also for removing the genarator from circuit relation with the called lne.

25. A telephoneexchange system including telephone lines extending from sub-stations to an exchange, link connectors at the exchange for unitin lines in conversation, a calling generator or operating the signal receivers at called stations, mechanism governed at a called station for removing, the signal generator from circuit with a called line, and operated when the called station responds, and electro-magnetic means operable by the calling station switch-hook when the receiver is placed thereupon Yalso for removing the generator from circuit relation with the called line. l

26. A telephone exchange system including telephone lines extending from sub-stations to an exchange, link connectors at the exchange for unitin lines in conversation, a calling generator or operating the signal receivers at called stations, electro-magnetic mechanism governed at a called station for removing the signal generator from circuit with a called line, and operated when the called station responds, and electro-magnetic means operable by the calling station switchhook when the receiver is placed thereupon, also for removing the generator from circuit relation with the called line.

27. A telephone exchange system including telephone lines extending from substations to an exchange, link circuits for uniting lines in conversation, a pair of disconnect signals for each link circuit, apparatus whereby one of said signals is associated with the calling line and is governed thereby to the exclusion of the called line, and apparatus whereby the other of said signals may pe operated by both the calling or called ine.

28. A common batter telephone exchange system including telep one lines extending from substations to an exchange, link connectors for uniting said lines in conversation, an operators telephone outt having a terminal provided with means for bringing it in physically continuous connection with a link conductor, and two meansjneluded in said link conductor, one on cach side of the connection of said operators telephone outfit terminal With said link conductor7 said means operating to prevent the passage of signal operating current through the operators telephone outfit.

Q9. A common battery telephone exchange system including telephone lines extending from substations to an exchange, link connectors for uniting said `lines in conversation, signaling apparatus in physically continuous connection With. a link conductor, a common battery for operating said signaling apparatus and also in physically continuous connection with said link conductor, a telephone having a terminal provided with means for bringing it in physically continuous connection with said conductor, and tWo means individual to and included in said link conductor, one on each side of the connection of said telephone terminal with said link conductor, said means operating to prevent the passage of signal operating current through the telephone. I

30. A common battery telephone exchange system including telephone lines extending from substations to an exchange, link connectors for uniting said lines in conversation, signaling apparatus in physically continuous connection with a link conductor, a common battery for operating said signaling apparatus and also in physically continuous connection with said link conductor, a telephone having a terminal provided with means for bringing it in physically continuous connection with said conductor, and tWo condensers individual to and included in said link conductor, one on each side of the connection of said telephone terminal with said link conductor, said condensers operating to prevent the passage of signal operating current through the telephone.

In witness whereof, I hereunto subscribe my name this 11th day of February A. D.',

ELMER R. CORWIN. Witnesses G. L. CRAGG, F. Gr. SfrRoH.

Copies of this patent may be obtained for ve cents each, by addressing the Commissioner of Twents, Washington, D. C. 

